Method and device for processing active microcrystalline fiber by magnetic field induction and lasering

A method of preparation of an active optical fiber, comprising:

• processing Yb:YAG crystals with a doping concentration of 10 at % into rods;
• polishing surfaces of the rods;
• inserting the rods into a clean and dried quartz sleeve to make a prefabricated rod;
• fixing the prefabricated rod on a laser drawing furnace with an aluminum fixture for wire drawings, thus yielding a drawn fiber;
• introducing the drawn fiber to pass through a magnetic field in an uncoated state, wherein two magnetic poles of the magnetic field are vertically placed on both sides of the drawn fiber, and the drawn fiber coincides with the central axis of the two magnetic poles;
• turning on a carbon dioxide laser at the same time as the step of introducing the drawn fiber;
• and
• focusing a laser beam of the carbon dioxide laser on the drawn fiber such that the drawn fiber is recrystallized to obtain the active optical fiber comprising a fiber core with a diameter ranging from 5-100 μm and a cladding layer with a diameter ranging from 120-800 μm, wherein the laser beam is focused and shaped into spots acting around the drawn fiber so that the drawn fiber is heated evenly and the fiber core is at the center of the cladding.